TUBE commuters using the borough's stations are being asked to be vigilant against possible terrorist attacks in London, following the bomb blasts in Madrid that claimed more than 200 lives.

As part of the continuing Government campaign against the threat from terrorism, police have stepped up patrols on the London Underground system including, for the first time, deploying plain clothes counter terrorist patrols to key locations. These measures were taken before Thursday's bomb explosions in Madrid and are not connected.

"This is a joint operation involving BTP, the Metropolitan Police, City of London Police and Transport for London,' explained Deputy Chief Constable Andy Trotter from the British Transport Police.

"I must emphasise that we have received no specific threat to the London Underground or rail system, nevertheless, the threat from terrorism remains very real as the events in Madrid show."

Police are appealing to passengers to be pro-active in reporting anything suspicious, asking other passengers if they see an item they believe to be unattended - "Who owns this bag?" - and reporting it immediately to London Underground staff or police if it is unclaimed.

Posters will be appearing on the London Underground system this week.

As part of the security regime, passengers may see police officers conducting "stop and search" procedures on stations.

"If passengers are subject to such searches, we would ask them to be patient in supporting the continuing fight against terrorism," CC Trotter said.

These measures come as leading security experts from Metro systems around the world met in London last week to review methods of combating terrorism at a conference hosted by the BTP, London Underground and its infrastructure partners Metronet and Tube Lines.

Anyone with information about terrorist activity can contact the free, confidential Anti-Terrorism hotline on 0800 789 321.

In an emergency dial 999.

We need more police' Train companies must pay for more British Transport Police following the tragic events in Madrid last week, according to Seema Malhotra, London Assembly Candidate for Hounslow.

Seema said "Labour Assembly members have been pressing for better policing of our overland rail stations for some months because of the anti social behaviour that many passengers have to suffer.

"The tragic events in Madrid underline how vital security is on our transport network. More British Transport Police would ensure that both day to day safety is tackled better and that catastrophic events like the Madrid bombings are less likely."

Seema's calls are backed by the chairman of the British Transport Police Federation, Alex Robertson, who is calling for the Government to increase the force by at least 200 more officers nationwide.

"The Mayor has significantly increased police numbers since he came to power and Transport for London has put extra funding directly into extra police on the tube.

"We now need to see similar commitment from the train operators to our overland rail.

"We need to break out of the mindset of minding our own business and be constantly aware that any baggage without an owner is a potential threat," she said.

London Mayor Ken Livingstone has increased police numbers by around 5,000 to over 30,000 since being elected in May 2000.

London Underground is funding extra British Transport Police to patrol across the tube network.

Over-ground policing is paid for through the subsidies given to train companies.

Operators have pledged CCTV at all stations along the line.